EarthTechling has a post on a wind turbine design that works well in light winds - Gearless Turbine Gets Power From Light Winds.
Windtronics has developed a new home wind turbine that could be a practical renewable energy option, even for folks living in areas with light or infrequent winds. The new product is called the Honeywell Wind Turbine and its manufacturer says it features technology capable of converting wind speeds as low as two mph into energy.
The Honeywell Wind Turbine weighs in at just under 185 pounds and measures about six feet in diameter. Windtronics claims it can produce up to 1500 kilowatt-hours annually depending on the wind speeds at a given location and the height at which the turbine is mounted.
Perhaps the turbine’s most unique design point is that it is totally gearless. Instead of gears, it uses a system of magnets and stators that line its outer ring to capture power at the blade tips where speed is greatest. According to Windtronics, this design practically eliminates mechanical resistance and drag thereby allowing the turbine to start turning in winds as low as 0.5 mph and generate energy at 2 mph.